Intake system for multi-cylinder combustion engines

ABSTRACT

An intake system for internal combustion engines with multiple cylinders, comprising a first air distribution chamber, one separate inlet pipe for each engine cylinder, which inlet pipes extend between the first distribution chamber and the respective inlet valve/valves of the corresponding cylinder, and a second air distribution chamber. The second chamber is connectable to each one of the inlet pipes between the first chamber and the inlet valves via a respective passage which passage can be opened by means of an operable valve. The valves are simultaneously operable between closed and open positions via control means with regard to the speed of the engine. The second air distribution chamber receives inlet air via an adjustable throttle valve. The first air distribution chamber is divided into two volumes, being connectable via an additional openable valve, wherein each volume is connected to the second distribution chamber via at least one resonance pipe. The valve of the first air distribution chamber is maneuverable between closed and open positions via control means with regard to the speed of the engine.

TECHNICAL FIELD

An intake system for internal combustion engines with multiplecylinders, comprising a first air distribution chamber, one separateinlet pipe for each engine cylinder, which inlet pipes extend betweenthe first distribution chamber and the respective inlet valve/valves ofthe corresponding cylinder, and a second air distribution chamber, whichis connectable to each one of the inlet pipes between said first chamberand the inlet valves via a respective passage which passage can beopened by means of an operable valve, which valves are simultaneouslyoperable between closed and open positions via control means with regardto the speed of the engine.

BACKGROUND OF THE INVENTION

EP 94850128.3 describes an active intake system for multiple cylindercombustion engines, comprising a first air distribution chamber, oneseparate inlet pipe for each engine cylinder, which inlet pipes extendbetween the first chamber and the respective inlet valve/valves of thecylinders. Also, there a second air distribution chamber which isconnectable to each one of the inlet pipes between said first chamberand the inlet valves via a respective passage which passage can beopened by means of an operable throttle valve. The second chamber isconnected to the first chamber via resonance pipes, the inlets to thesecond chamber being openable via a further throttle valve. Thissolution enables exploitation of the resonance frequency for anadvantageous volumetric efficiency within the middle and upper enginespeed ranges.

In many cases, it is desirable to instead provide a more advantageousvolumetric efficiency within a lower range of engine speed. This isrelatively simple to accomplish, but in that case it is normal to get adip in the moment curve effecting the middle range of the engine speed.Such a dip is perceived by the driver of a vehicle, as if the enginelacks power in the middle range. Therefore, the normal driver tends touse unnecessary high revs in order to keep the engine out of the dip inthe moment curve. This results in that the positive effect of theincreased volumetric efficiency in reality disappears for these knownarrangements.

THE TECHNICAL PROBLEM

The object of the present invention is therefore to provide an intakesystem which offers a more advantageous volumetric efficiency within alower range of engine speed, without affecting the middle range ofengine speed.

THE SOLUTION

This has been achieved according to the invention in that the second airdistribution chamber receives inlet air via an adjustable throttlevalve, in that the first air distribution chamber is divided into twovolumes, being connectable via an additional openable valve, whereineach volume is connected to the second distribution chamber via at leastone resonance pipe, and in that the valve of the first air distributionchamber is manoeuvrable between closed and open positions via controlmeans with regard to the speed of the engine.

Advantageous variants of the invention are disclosed in the accompanyingsubclaims.

DESCRIPTION OF THE DRAWINGS

The invention will be described more in detail in the following, withreference to embodiments shown in the enclosed drawings, on which

FIG. 1 discloses schematically an intake system according to theinvention, which is adapted to a six-cylinder combustion engine,

FIG. 2 is a diagram, which illustrates the technical effect of theintake system according to the invention,

FIG. 3 shows in the same manner as FIG. 1 an intake system which isadapted for a four-cylinder combustion engine, and

FIG. 4 shows an alternative design of the first air distribution chamberand the resonance pipes.

DESCRIPTION OF EMBODIMENTS

FIG. 1 discloses an intake system for a six-cylinder internal combustionengine 10. The intake system comprises an outlet spigot 11 from a notdisclosed air filter housing. A throttle valve 12 is provided in theoutlet spigot, for control of the flow volume of the filtered intakeair.

The outlet spigot 11 opens out into an air distribution chamber 13 whichis located in connection with inlet pipes 14 extending between the inletvalve/valves of each motor cylinder and an additional air distributionchamber 15. This chamber 15 is divided by means of a partition wall 16into two acoustically substantially equal volumes 17a, 17b. Thepartition wall 16 is provided with an openable valve 18 which enablesfor the two volumes to be acoustically interconnected into a commonvolume.

Each of the two volumes 17a, 17b of the chamber 15 is connected to thechamber 13 via a resonance pipe 19. Also, each of the six inlet pipes 14is provided with its own passage into the chamber 13 which passage canbe opened by means of a valve 20. Preferably, the resonance pipes haveequally long acoustic length as those segments of the inlet pipes 14which extend between the passage valves 20 and the chamber 15. On thecontrary, the acoustic cross sectional area of the resonance pipes 19differ from the acoustic cross sectional area of the inlet pipes 14.Preferably, the passage valves 20 are located at about one third of thedistance from the motor 10 to the chamber 15.

The valve 18 can be operated between open and closed position via a notshown micro processor. This processor receives input which is based uponthe speed of the engine, so that changeover from one mode to the otheroccurs automatically at a certain engine speed. In a corresponding way,the passage valves 20 can be operated simultaneously automaticallybetween closed and open positions via corresponding control means withregard to the speed of the engine.

FIG. 2 illustrates graphically the function of the inlet system, whereinthe horizontal axis indicates increasing number of revolutions r/s andthe vertical axis indicates increasing torque Nm.

Within a low range of engine speed, which is illustrated by the graph21, an advantageous torque is obtained with closed valves 18 and 20.Hereby the oscillation period of the air volume in the intake system isdetermined by the acoustic length of the inlet pipes 14, the air volumein the chamber section 17a and 17b respectively, the air volume in therespective resonance pipes 19 and the air volume in the chamber 13.

Within a medium range of engine speed, which is illustrated by the graph22, an advantageous torque is obtained with the valve 18 in its openposition. Hereby the oscillation period of the air volume in the inletsystem is determined by the acoustic length of the inlet pipes 14.

Within a higher range of engine speed, which is illustrated by the graph23, an advantageous torque is obtained with the valves 18 and 20 open.Hereby the oscillation period of the air volume in the inlet system isdetermined by the acoustic length of the first third of the resonancepipes 14.

As FIG. 2 illustrates, it is also possible to use a mode of operation inaccordance with graph 21, after passing the peak of graph 22, wherein amore even transition to graph 23 is obtained.

Preferably, all valves 20 are arranged along a common shaft, so thatthey are opened and closed simultaneously.

FIG. 3 discloses a alternative embodiment of the intake system which isadapted for a four-stroke internal combustion engine having four in-linecylinders. The inlet pipes 14 to both end cylinders are connected to oneof the chamber volumes 17a, and the intake pipes 14 to the twointerjacent cylinders are connected to the second chamber volume 17b.This involves making the inlet pipe 14 for one of the two outercylinders cross the inlet pipes of the two interjacent cylinders.However, the inlet pipes run the shortest distance between the motor andthe valves to the chamber 13.

FIG. 4 shows still another embodiment of the inlet system, in which theresonance pipes 19 are centrally located between two groups of inletpipes 14. This figure shows that the valve 18 of the first airdistribution chamber 15 does not have to be located inside the first airdistribution chamber 15, but instead may form an openable connectionbetween the resonance pipes 19 at a suitable location between the twoair distribution chambers 13, 15.

The invention is of course not limited to the disclosed embodiments, buta number of modifications are conceivable within the scope of thefollowing claims, and consequently the invention can of course also beapplied to engines with other cylinder configurations than in the shownembodiments. Further, the first air distribution chamber may be designedin many different ways, e.g. as two separate units, which areinterconnected via an openable passage of suitable length.

I claim:
 1. An intake system for internal combustion engines withmultiple cylinders, comprising a first air distribution chamber, oneseparate inlet pipe for each engine cylinder, which inlet pipes extendbetween the first distribution chamber and a respective inlet valve ofthe corresponding cylinder, and a second air distribution chamber, whichis connectable to each one of the inlet pipes between said first chamberand the inlet valves via a respective passage which is operable by wayof respective valves, which valves are simultaneously operable betweenclosed and open positions via control means which operate the valvesbased on the speed of the engine, the second air distribution chamberreceiving inlet air via an adjustable throttle valve, the first airdistribution chamber being divided into two volumes that are connectablevia an additional openable valve, and the valve of the first airdistribution chamber being maneuverable between closed and openpositions via control means which operate the valve based on the speedof the engine.
 2. An intake system according to claim 1, wherein theintake system is operational in three operational modes, wherein in afirst mode of operations, both the passage valves and the valve of thefirst air distribution chamber are in a closed position, in a secondmode of operation, the passage valves are in a closed position and thevalve of the first air distribution chamber is in the open position, andin a third mode of operation, the passage valves are in an open positionand one valve of the first air distribution chamber is in an openposition.
 3. An intake system according to claim 1, wherein the passagevalves are mounted on a common maneuvering shaft.
 4. An intake systemaccording to claim 1, wherein the two volumes are connected to thesecond air distribution chamber by resonance pipes, the resonance pipeshaving the same acoustic length as the acoustic length of the inletpipes between the first and the second air distribution chamber.
 5. Anintake system according to claim 1, wherein the two volumes areconnected to the second air distribution chamber by resonance pipes theacoustic cross-sectional area of the resonance pipes differs from theacoustic cross-sectional area of the inlet pipes.
 6. An intake systemaccording to claim 1, adapted to a four cycle combustion engine havingfour in-line cylinders, the inlet pipes to both end cylinders beingconnected to one of the volumes, and the intake pipes to the twointerjacent cylinders being connected to the second chamber volume.